Process for recovery of metals from their ores



Patented Jan, 1, 1924.

UNITED STATES PATENT OFFICE.

WILHELM HIRSCHKIND, OF LOS ANGELES, CALIFORNIA, AS SI GNOR F ONILHALF TO INTERNATIONAL PRECIPITATION COMPANY, OF LOS ANGELES. CALIFORNIA, A

CDBPORATION OF CALIFORNIA.

PROCESS FOR RECOVERY OF METALS FROM THEIR ORES,

No Drawing.

To all whom it may concern:

-Be it known that 1, Human Hlnsrir KIND, a citizen of the l nitcd States, residin at Los Angeles, in the county of Los Angeles and State of California, have invented a new and useful Process for Rccov cry of Metals from Their Ores, of which the following is a specification.

This invention relates to the recovery of l0 metals such as gold, silver and mercury from ores thereof, by solution of the metal lic values in cyanide solution and precipitzu tion of the metals from such solution.

Another object of the invention is to provide for carrying; on the precipitating open ation in such manner as to regenerate sodium cyanide or other alkali metal cyanide in the solution.

The main object of the present invention is to effect the precipitation of metals from the cyanide solution by means of a readily soluble reducing compound in place of the metallic agents such as zinc dust or shavings, and aluminum dust.

I have discovered that sodium hydrosulfite (sodium hyposulfite) having, a composition represented by the formula Na S O, will precipitate metals such as gold, silver, or mercury, from cyanide solution with re generation of the sodium cyanide according to the reaction: 23 aAg(CN). .+Na S,O, 2Ag+4NaCN+SO,. The sulfurdioxidc produced by the reaction combines with the alkali present in the cyanide solution forming sulfites. The sodium cyanide is completely re enerated to be used over and over again. I in any case the presence of the sulfites formed from the sulfurdioxide and the alkali in solution is inimical to the effective reuse of the barren liquor in cyclic operation of the process such Snlfite may be eliminated from the solution in any suitable manner as, for instance, it may be oxidized to form sodium sulfate or precipitated with lime as calcium 'sulfite.

Further details and advantages of my process may be stated as follows:

The cyanide solution of gold, silver, mercur or any two or more of these metals is 60 ma e up in any usual or suitable manner by subjectinp the ore to the leaching action of the solution containing alkali metal cyanide, for example, sodium cyanide, in the presence of any agents which may be Serial No. 540,565.

caustic soda or caustic lime, lead salts, oxygen supplied by bubbling air through tlia solution, etc. After the extraction of the metals by the cyanide solution has proceed-- ed as far us practicable, the nietal-carryin solution is separated from the ore am passed to suitable precipitating apparatus where it is subjected to the precipitating operation. The sodium hydrosulfite is added either in form of a solution or in solid form to the pregnant solution in the precipitating apparatus. inasmuch as sodium hydrosullitc absorbs oxygen very rapidly. it is desirable to remove the oxygen from the pregnant solution as far as pos sible in order to use the least quantity of precipitating agent. This may he accomplished by subjecting the solution to a vacuum or otherwise.

Through the action of the hydrosulfite, the metals are precipitated in pure form and settle. to the bottom of the precipitating apparatus. They may be separated from the liquid by filtration or decantation, and the liquor may be returned to the leaching apparatus. Any desired modifying agent such as caustic soda. caustic lime. lead salt, oxygen (furnished by bubblin air through the solution), etc. may be added, before or during the extraction process, to the solution so returned.

An important advantage of the process as above described is that the gold and silver, for example. being: precipitated in substantially pure condition free from any solid precipitating agent such as zinc, can be melted down into bullion, which is substan tially' pure as distinguished from the comparatively impure bullion resulting from the meltin down of the precipitate pro duced by zinc dust or zinc shavings.

In lace of sodium hydrosulfite, other soluble hydros lfitcs may be used, for example, any hydrosulfite of an alkali or alkaline earth metal.

What I claim is:

1. The process which consists in precipitatin gold, silver or other metal from cyani e solution thereof by adding to such solution sodium hydrosulfite. 2. The process which consists in mung on a cyanide solution of gold, silver or other metal with a soluble hydrosulfite so as to precipitate the said metal in metallic form.

3. The rocess which consists in precipitating go (1, silver, or other metal from an alkaline cvanide solution thereof, by adding a soluhle hydrosulfite to such solution, and separ atin the resulting from the solution.

4. The process which consists in adding alkali metal hydrosulfite to an alkaline cyanide solution of gold, silver, or otheimetal, so as to precipitate the said metal and to produce alkali metal cyanide, separating tie prei itete from the solution, utilizing the resi ual solution in leaching an precipitate ore of such metal, to produce an alkaline cyanide solution of such metal for cyclic operation of the process.

5. The process which consists in'leaching an ore of gold, silver or other metal with sodium cyanide solution to produce an ulka line cyanide solution of such metal, adding sodium hydrosulfito to the solution to precipitate such metal and to produce sodium cyanide in the solution, separating the precipitate from the solution, and utilizing the solution. in cyclic operation of the process.

In testimony whereof I have hereunto subscrib d my name this 20th day of February, 1922.

WILHELM HIRSCHKIND. 

